Large-scale purification of factor VIII by affinity chromatography: optimization of process parameters

The optimization of a new process for the extraction of human coagulation factor VIII (FVIII) from plasma with the tailor-made affinity matrix dimethylaminopropylcarbamylpentyl-Sepharose CL-4B (C3---C5 matrix) is described. First, plasma is applied to DEAE-Sephadex A-50 anion exchanger in order to separate a number of proteins, including coagulation factors II, IX and X (prothrombin complex), from FVIII. Subsequently, the unbound fraction of the ion exchanger, containing FVIII, is contacted with the C3---C5 affinity matrix. Optimization of the FVIII affinity chromatographic procedure is accomplished in terms of the ligand density of the matrix, adsorption mode (batch-wise versus column-wise adsorption and matrix to plasma ratio), and conditions of pH and conductivity to be applied on washing and desorption. In scale-up experiments, by processing 20 1 of plasma, the recovery (340 U VIII:C/kg plasma) and the specific activity (s.a.) (1.2 U VIII:C/mg protein) are better than those obtained by cryoprecipitation (recovery 300 U VIII:C/kg plasma, s.a. O.3 U VIII:C/mg protein). The newly developed process using the specially designed C3---C5 affinity matrix has potential application in the process-scale purification of FVIII

Effects of Population Based Screening for Chlamydia Infections in The Netherlands Limited by Declining Participation Rates

Background: A large trial to investigate the effectiveness of population based screening for chlamydia infections was conducted in the Netherlands in 2008-2012. The trial was register based and consisted of four rounds of screening of women and men in the age groups 16-29 years in three regions in the Netherlands. Data were collected on participation rates and positivity rates per round. A modeling study was conducted to project screening effects for various screening strategies into the future. Methods and Findings: We used a stochastic network simulation model incorporating partnership formation and dissolution, aging and a sexual life course perspective. Trends in baseline rates of chlamydia testing and treatment were used to describe the epidemiological situation before the start of the screening program. Data on participation rates was used to describe screening uptake in rural and urban areas. Simulations were used to project the effectiveness of screening on chlamydia prevalence for a time period of 10 years. In addition, we tested alternative screening strategies, such as including only women, targeting different age groups, and biennial screening. Screening reduced prevalence by about 1% in the first two screening rounds and leveled off after that. Extrapolating observed participation rates into the future indicated very low participation in the long run. Alternative strategies only marginally changed the effectiveness of screening. Higher participation rates as originally foreseen in the program would have succeeded in reducing chlamydia prevalence to very low levels in the long run. Conclusions: Decreasing participation rates over time profoundly impact the effectiveness of population based screening for chlamydia infections. Using data from several consecutive rounds of screening in a simulation model enabled us to assess the future effectiveness of screening on prevalence. If participation rates cannot be kept at a sufficient level, the effectiveness of screening on prevalence will remain limited

Towards an Intrinsic Doppler Correction for X-ray Spectroscopy of Stored Ions at CRYRING@ESR

We report on a new experimental approach for the Doppler correction of X-rays emitted by heavy ions, using novel metallic magnetic calorimeter detectors which uniquely combine a high spectral resolution with a broad bandwidth acceptance. The measurement was carried out at the electron cooler of CRYRING@ESR at GSI, Darmstadt, Germany. The X-ray emission associated with the radiative recombination of cooler electrons and stored hydrogen-like uranium ions was investigated using two novel microcalorimeter detectors positioned under 0∘ and 180∘ with respect to the ion beam axis. This new experimental setup allowed the investigation of the region of the N, M → L transitions in helium-like uranium with a spectral resolution unmatched by previous studies using conventional semiconductor X-ray detectors. When assuming that the rest-frame energy of at least a few of the recorded transitions is well-known from theory or experiments, a precise measurement of the Doppler shifted line positions in the laboratory system can be used to determine the ion beam velocity using only spectral information. The spectral resolution achievable with microcalorimeter detectors should, for the first time, allow intrinsic Doppler correction to be performed for the precision X-ray spectroscopy of stored heavy ions. A comparison with data from a previous experiment at the ESR electron cooler, as well as the conventional method of conducting Doppler correction using electron cooler parameters, will be discussed

Metallic Particle Motion and Breakdown at AC Voltages in CO₂/O₂ and SF₆

This study deals with gaseous insulation contaminated by free moving particles. Two gases were investigated: SF6 (0.45 MPa) and a CO2/O2 gas mixture (0.75 MPa). Video recordings were used to track a free particle moving between a plate and a Rogowski electrode for validation of a 1D particle motion model. The effect of fixed and free particles (4 or 8 mm, Ø 0.9 mm) on the breakdown voltage and the mean time between breakdowns was determined in a concentric set of electrodes. The value of the breakdown voltage for a free particle was between those of a particle fixed to the enclosure and the central electrode. The particle motion in the concentric case could not be observed in the experimental set-up and was therefore simulated using a 1D model. For the 4 mm free particle, the breakdown seemed to be initiated in the inter-electrode gap in CO2 and at the crossing in SF6, while for the 8 mm particle, breakdown occurred at lift-off in both gases. A parameter k describing the width of the time to breakdown distribution was introduced. A low value of k was associated with the breakdown from the particles at the electrodes, while k was larger than 10 when the breakdown was decided during particle flight

Human platelet 6-phosphofructokinase . Relation between inhibition by Mg · ATP2 - and cooperativity towards fructose 6-phosphate and investigations on the formation of a ternary complex

Human platelet 6-phosphofructokinase (EC 2.7.1.11) shows cooperativity towards Fru-6-P and is allosterically inhibited by high Mg . ATP2− concentrations. No relation could be demonstrated between the cooperativity towards Fru-6-P and the inhibition by Mg . ATP2−. Increasing the concentrations of Mg . ATP2− only raised the apparent Km values for Fru-6-P, but did not change the Hill constants. a possible formation of a Mg . ATP2− : enzyme . Fru-6-P complex during catalysis was investigated. Our calculations suggest that such a ternary complex is indeed formed during the reaction

In situ studies of the oxidation of HCl over RuO2 model catalysts: Stability and reactivity

Structure–activity experiments were performed for the HCl oxidation reaction (Deacon-like process) over RuO2 model catalysts – RuO2(1 1 0) and RuO2(1 0 0) – applying in situ surface X-ray diffraction (SXRD) combined with on-line mass spectrometry. The studied model catalysts turned out to be long-term stable under reaction conditions with gas feed ratios p(HCl):p(O2) ranging from 1:4 to 4:1 in the mbar pressure regime and temperatures as high as 685 K. Even pure HCl exposure in the mbar regime was not able to reduce RuO2 below 600 K; above 650 K chemical reduction of the oxide sets in. Under strongly oxidizing reaction conditions, the (surface) oxides grow slowly in thickness. On-line reactivity experiments of both types of model catalysts in a batch reactor yield a mean turn-over frequency (TOF) of 0.6 Cl2 molecules per second and active site for the HCl oxidation at 650 K and initial partial pressures of p(HCl) = 2 mbar and p(O2) = 0.5 mbar. The HCl oxidation over RuO2 is therefore considered to be structure insensitive

INLO-PUB-15/95 3 October, 1995 Does a Metal Spoon improve the Quality of

We investigated the verity of a wide-spread folk wisdom that left-over sparkling wine is conserved much better with a metal spoon hanging in the neck of the bottle. In a carefully controlled experiment we do not find any measurable improvement in the shelf life time of cider